The invention relates to an optical apparatus comprising an optical component, in particular a lens, which is mounted in a socket and has at least one optical surface, wherein stresses within the component are set or can be varied by means of manipulators.
The invention further relates to a method for influencing a polarization state of an optical component of an illumination system and/or of a projection objective in a microlithographic projection exposure apparatus.
U.S. Pat. No. 6,307,688 B1 discloses the use of actuators for an optical component, in particular a lens, which act in the radial direction in order to produce pulling or pushing forces. In this case, T-shaped levers are used in the area between an inner holding ring, which holds the lens, and an outer socket, via which forces are introduced to the holding ring. The forces can also be produced piezoelectrically or by means of hydraulic units, instead of mechanical force production.
US 2003/0095345 A1 discloses holders for a lens, in which the lens is not held in radial direction, in order to prevent deformations.
A lens with a variable focal length is described in U.S. Pat. No. 6,246,528 B1. The lens comprises two optical boundary surfaces and, between them, a synthetic, elastically deformable and transparent refraction body, which can be stressed via actuators which act in the radial direction, for example by micrometer screws, on its side periphery. The lens is itself composed, for example, of piezoelectric material. Alternatively, a ring is used which surrounds the lens and is composed of a magnetostrictive material. A bimetallic ring can also be used, which changes its shape at a specific transition temperature. In the same way, hydraulic or pneumatic cylinders or magnet coils can also be used in order to influence the periphery of the refraction body. In one refinement of the lens (FIG. 8), provision is made for radially mounted manipulators to exert torques on the lens in the direction of the optical axis. The concept which is described in U.S. Pat. No. 6,246,528 B1 refers back to U.S. Pat. No. 1,269,422.
A stressed refraction mirror according to U.S. Pat. No. 5,552,006 comprises a stressing device with a large number of pneumatic cylinders, which are arranged distributed over the entire circumference of the side edge of the refraction mirror.
U.S. Pat. No. 4,327,984 describes a design with a lens, to which stress can be applied by means of radially aligned screws. Stress is also applied to a lens in the radial direction by means of a large number of clamping means according to JP 2001284226 A.